rename: the server is Inkwell — package, env vars, image, compose, export marker

Step 2 of milestone 481. The operator chose a full rename (Scribe note 5071), so
this goes past the display strings into the identities:

- src/thoughtsync → src/inkwell; every import, the Dockerfile and both compose
  commands, alembic env, pyproject
- THOUGHTSYNC_* → INKWELL_* (database URL, secret key, log level, tag/port/bind)
- container data dir /var/thoughtsync → /var/inkwell
- image git.fabledsword.com/bvandeusen/inkwell; Postgres user/db default inkwell;
  CI's integration service follows
- the files the image serves are inkwell.*. fetch-clients.sh still fetches the
  thoughtsync-named release assets, because the lanes that publish them are
  renamed in steps 3 and 4
- exports are written with app "inkwell"

Two deliberate exceptions, both because data rides on them:

- compose volumes are now named explicitly and overridable (INKWELL_DB_VOLUME,
  INKWELL_DATA_VOLUME), so a deployment installed as ThoughtSync points at the
  volumes and DB identity it already has. .env.example says exactly what to set
- import still accepts app "thoughtsync", because exports written before the
  rename are backups. Tested both ways

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -54,7 +54,7 @@ permissions:
 
 env:
   REGISTRY: git.fabledsword.com
-  IMAGE: git.fabledsword.com/bvandeusen/thoughtsync
+  IMAGE: git.fabledsword.com/bvandeusen/inkwell
 
 jobs:
   # Should this push build an image now, or is the Android lane about to publish a
@@ -215,11 +215,11 @@ jobs:
         # Postgres it will actually meet.
         image: postgres:16-alpine
         env:
-          POSTGRES_USER: thoughtsync
+          POSTGRES_USER: inkwell
           POSTGRES_PASSWORD: ci_integration
-          POSTGRES_DB: thoughtsync_test
+          POSTGRES_DB: inkwell_test
         options: >-
-          --health-cmd "pg_isready -U thoughtsync"
+          --health-cmd "pg_isready -U inkwell"
           --health-interval 10s
           --health-timeout 5s
           --health-retries 10
@@ -243,7 +243,7 @@ jobs:
           test -n "$PG"
           PG_IP=$(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$PG")
           test -n "$PG_IP"
-          export THOUGHTSYNC_DATABASE_URL="postgresql+asyncpg://thoughtsync:ci_integration@${PG_IP}:5432/thoughtsync_test"
+          export INKWELL_DATABASE_URL="postgresql+asyncpg://inkwell:ci_integration@${PG_IP}:5432/inkwell_test"
           # Wait for Postgres to accept connections. `run:` is busybox sh (rule 81) —
           # no bash /dev/tcp — so use the Python that is always present here.
           /opt/venv/bin/python - "$PG_IP" <<'PY'